Description: (Taken directly from the application) The objective of this research is to develop and test therapies for autosomal recessive polycystic kidney disease (ARPKD), which are specifically designed to target key processes in disease pathogenesis. The overall hypothesis to be tested is that interruption or therapeutic targeting of abnormalities in the epidermal growth factor (EGF)-transforming growth factor alpha (TGF-alpha) epidermal growth factor receptor (EGFR) axis in ARPKD will result in structural and functional improvement in cystic kidney disease. Published data from a number of laboratories demonstrate that altered EGFR expression in cystic tubular epithelial cells is common to human and murine ARPKD as well as autosomal dominant polycystic kidney disease (ADPKD). Although the specific projects proposed will focus on animal models of ARPKD and human ARPKD cells, therapies developed during the course of this study may be generalizable to ADPKD as well. Studies will be conducted in primary and immortalized cell lines, organ culture and intact animals. Pharmacologic, genetic and cell biology techniques will be employed to accomplish the following Specific Aims: 1. Develop therapeutic strategies aimed at interrupting EGF-TGFalpha-EGFR axis activity in ARPKD. Specific hypotheses to be tested are: a.) Inhibition of EGFR activity results in sustained improvement of renal function without toxicity in ARPKD; b.) Inhibition of the production and/or processing of biologically active ligands (EGF/TGFalpha ) has therapeutic effectiveness in ARPKD: and c.) Combined inhibition of EGFR activity and processing/production of EGF/TGFalpha is more effective and less toxic than either therapy given alone. Methods to be utilized in the proposed studies include in vitro/vivo trials of EGFR tyrosine kinase inhibitors, agents which alter ligand production, and antisense oligonucleotides. 2. Develop new strategies for gene therapy in ARPKD. Specific hypotheses to be tested are: a.) Gene replacement following disease development can alter disease progression in ARPKD; b.) Effectiveness and specificity of gene therapy can be improved by utilizing elements of the EGF/TGFalpha /EGFR axis to augment gene delivery; and c.) Genetic therapy directed at targeting key pathogenic processes following disease development can alter disease progression in ARPKD. Methods to be utilized in the proposed studies include liposome mediated gene transfer, adeno-associated virus-mediated gene transfer, and the use of EGFR-ligand or antibody to deliver genes by receptor mediated endocytosis. These studies will provide new scientific insights and information which may be useful in the design of specific treatments for human ARPKD and ADPKD.